feat: add minimal plugin scaffold

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

KimaiHeatmapBundle.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace KimaiPlugin\KimaiHeatmapBundle;
+
+use App\Plugin\PluginInterface;
+use Symfony\Component\HttpKernel\Bundle\Bundle;
+
+class KimaiHeatmapBundle extends Bundle implements PluginInterface
+{
+}

composer.json

@@ -0,0 +1,17 @@
+{
+    "name": "kimai-plugin/heatmap-bundle",
+    "type": "kimai-plugin",
+    "description": "GitHub-style activity heatmap dashboard widget for Kimai",
+    "license": "MIT",
+    "autoload": {
+        "psr-4": {
+            "KimaiPlugin\\KimaiHeatmapBundle\\": ""
+        }
+    },
+    "extra": {
+        "kimai": {
+            "require": 25200,
+            "name": "Activity Heatmap"
+        }
+    }
+}